fix(ego-browser): probe the installed skill location for the agent workspace

[Hotragn]

Summary

In the app-bundled CLI the agent-workspace fallback resolves to a path that does not exist (from a root cwd, literally /skills/ego-browser), so the entire site-learnings subsystem is unreachable even though the learning packs ship with the app and are present on disk. This PR keeps the existing resolution precedence and adds one narrow step: when neither module-relative candidate exists on disk, probe the user-level location onboarding registers, accepting it only when it actually holds learnings/.

Related issue

Fixes the runtime-side root cause reported in #215. Note the reporter self-closed that issue (before this PR opened) after finding the in-process process.env.EGO_BROWSER_AGENT_WORKSPACE = ... workaround — the resolution defect itself is still present on dev, and this PR makes the workaround unnecessary for the CLI half. The app-side half (caller env not forwarded into the embedded runtime) remains out of this repo's reach.

Changes

• src/env.ts — agentWorkspace() keeps the current precedence (env override → skill bundled next to the build output → repo layout). New behavior only starts where the old chain returned a nonexistent path: when neither module-relative candidate exists, it probes ~/.local/share/ego/ego-skills (the location onboarding links, per the report in [Bug]: Site learnings unreachable — agent workspace falls back to /skills/ego-browser (filesystem root) in the bundled CLI #215) both as the skill directory itself and as a parent of ego-browser/. A candidate is accepted only when it holds learnings/, so a stale leftover directory cannot claim the workspace. When nothing exists anywhere, the returned value is byte-identical to today's (the repo-layout path).
• The home directory is resolved from HOME / USERPROFILE directly rather than through resolvePath("~..."), deliberately: the ~-expansion defect in resolvePath is already being fixed by fix(ego-browser): expand ~ paths to the home directory instead of the filesystem root #146 and fix(ego-browser): make the repo build, test, and commit on Windows #148, and this PR must not collide with either.
• agentWorkspace() gains an injectable { env, exists } seam (defaulting to process.env / existsSync) so the bundled-runtime layout is testable without touching the real filesystem — same injectable-seam pattern as update-notice.ts. All call sites are unchanged (agentWorkspace()).
• src/env.test.mjs — 8 regression tests covering the full decision table: override precedence, bundled candidate, repo-layout candidate, installed-root fallback, ego-browser/ subdirectory priority, rejection of an installed directory without learnings/, USERPROFILE resolution, and the nothing-exists default.

Note: prettier normalized two pre-existing unformatted blocks in env.ts (resolvePath, loadEnvFile) because the changed-file style gate checks whole files. Same situation #148 documented.

Verification

Run from package/ego-browser (Windows 11, Node 24; suite is platform-neutral):

npm test                      -> 319 pass, 0 fail (311 existing + 8 new)
npm run typecheck             -> ok
npm run validate:site-skills  -> site skills ok
npm audit --audit-level=moderate -> 0 vulnerabilities
prettier --check src/env.ts src/env.test.mjs -> ok

The new tests fail without the fix: reverting the src/env.ts change makes "falls back to the installed skill registered by onboarding", "prefers an ego-browser subdirectory inside the install root", and "resolves the home directory from USERPROFILE" fail (the old chain returns the repo-layout path).

I don't have a macOS install to run the shipped app against; the repro and paths come from the detailed report in #215. Behavior for repo checkouts is covered by the tests and unchanged.

Impact

• Public helper API or behavior
• Agent skill or instructions
• Site learning
• Installation or update flow
• Build, CI, or release process
• Documentation only
• No externally visible impact

Behavior change is strictly additive: the fallback only fires where the previous result was a nonexistent directory, so learnContext() / runSiteTool / runSiteBrowserTool start working in the app-bundled CLI without EGO_BROWSER_AGENT_WORKSPACE. Repo checkouts, the env override, and the SDK path resolve exactly as before. Composes cleanly with #146/#148 (different functions in the same file; no shared hunks beyond formatting).

Checklist

• The PR targets the correct base branch (dev for normal changes; only dev may target main).
• The change is focused and does not include unrelated cleanup.
• Tests were added or updated for behavior changes, or the reason they are unnecessary is explained above.
• Relevant tests and validation commands pass locally.
• Public helper JSDoc and agent-facing documentation are updated when the helper surface changes.
• No credentials, tokens, cookies, personal data, or other secrets are included.
• A release-note label is selected (fix).

[Hotragn]

Freshness check, since this has been open a while and the tree has moved elsewhere: the defect is still present on the active line.

package/ego-browser/src/env.ts on sprint-1.3.0 (currently c1b1184) is byte-identical to dev in the part this PR changes — agentWorkspace() still returns resolve(REPO_ROOT, "..", "..", "skills", "ego-browser") unconditionally when the bundled-sibling probe misses, which is how the search root becomes /skills/ego-browser in the app-bundled runtime (the report in #215).

So unlike #224/#251/#252 — whose files the rearchitecture removes — this one applies unchanged to whichever branch you take it on. It is still green and conflict-free against dev, and I have a sprint-1.3.0-based rebase ready if you would rather have it there; one word and I will retarget instead of opening anything new.

(The ~-expansion defect in the same file is also still present on sprint-1.3.0; that half belongs to #146/#148 and this PR deliberately stays clear of it.)

[Hotragn]

Rebased onto the active line and re-verified. agentWorkspace() on 2.0.0-beta-dev (a25f488) still returns resolve(REPO_ROOT, .., .., skills, ego-browser) unconditionally when the bundled-sibling probe misses, so the defect this fixes is present there too — not just on dev.

A v2-ready branch is pushed: https://github.com/Hotragn/ego-lite/tree/beta/agent-workspace (branched from a25f488, 8/8 new tests pass). One adaptation was needed: env.ts no longer exports SRC_DIR/REPO_ROOT on that line, so the test derives those paths from the built module's own location rather than widening the module's public surface for a test.

I could not open a PR for it — 2.0.0-beta-dev refuses CreatePullRequest from forks, while the same account opens PRs against dev normally (details in #312). Happy to send it wherever you prefer, or you can pull the branch directly. This PR remains valid for the dev line as-is.